/*
 * Copyright (c) 2023-2025 elsfs Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.elsfs.cloud.common.mybatis.ext.sql.support.union;

import org.elsfs.cloud.common.mybatis.ext.sql.SqlFragment;
import org.elsfs.cloud.common.util.lang.StringUtils;

/** 联合项 */
public interface UnionItem extends SqlFragment {

  /**
   * 剔除条件SQL头部多余的关键词
   *
   * @param unionSql 联合SQL
   * @return 合理的联合SQL
   */
  static String stripHeaderKeyword(String unionSql) {
    if (unionSql.startsWith("UNION ")) {
      return StringUtils.strip(unionSql, "UNION ");
    }

    if (unionSql.startsWith("UNION ALL ")) {
      return StringUtils.strip(unionSql, "UNION ALL ");
    }

    return unionSql;
  }
}
